Flat rotary pump



March 25, 1952 s, s, CHANG 2,590,435

FLAT ROTARY PUMP Filed April 29, 1950 3 Sheets-Sheet 1 ATTO RN EYS.

March 25, 1952 s s, CHANG 2,590,435

FLAT ROTARY PUMP Filed April 29, 1950 3 Sheets-Sheet 2 16.14. I I INVENTOR. v BY MM 4/4;

ATTCRN EYS.

March 25, 1952 s. s. L. CHANG FLAT ROTARY PUMP 3 Sheets-Sheet 5 FiledApril 29, 1950 INVENTOR. SHELDON 5. L. CH NG,

ATTORNEYS Patented Mar. 25, 1952 UNITED STATES PATENT OFFICE FLAT ROTARYPUMP Sheldon S. L. Chang, Springfield, Ohio, assignor to Robbins &Myers, Inc., Springfield, Ohio, a

corporation of Ohio Application April 29, 1950, Serial No. 159,077

15 Claims. 1

This invention relatesto a pump having relatlvely flat, disc-likepumping elements wherein the pumping elements are provided with spiralthreads and wherein one of the elements has one thread more than theother element. In the particular embodiment to be disclosed herein thestator element is shown as-having a double thread while the rotor isshown as having a single thread. Reference is made to the copend ingapplication of Byram and Chang, Serial No. 159,078, filed April 29,1950, and copending herewith wherein there is a general disclosure ofpumps of the type here under discussion. Reference is also made to thecopending application of Chang and Hagerman, Serial No. 146,334, filedFebruary 25, 1950, now Patent No. 2,566,116 issued August 28, 1951,wherein there is disclosed a machine for forming the pumping elements ofthe pump here under consideration.

It is an object of the present invention to provide a rotor surface anda stator surface which will function together to provide pumping pocketsfor conveying material to be pumped through the pump. The foregoing andother objects which will appear more fully hereinafter or which will beset forth specifically I accomplish by that construction and arrangementof parts of which I shall now disclose several exemplary embodiments.Reference is made to the drawings forming a part hereof and in which:

Figure 1 is a central longitudinal cross sectional view through a pumpemploying pumping elements according to the present invention.

Figure 2 is a plan view of a rotor according to the present invention.

Figure 3 is a cross sectional view of the same taken on the line 3-3 ofFigure 2.

Figure 4 is a plan view of a stator according to the present invention.

Figure 5 is a cross sectional view of the same taken on the line 55 ofFigure 4.

Figure 6 is a diagram to assist in an understanding of how the surfaceof a rotor is generated.

Figure 7 is a diagrammatic view in cross section of a rotor generatedaccording to Figure 6.

Figure 8 is a view similar to Figure 6 showing a different type of rotorin the process of bein generated.

Figure 9 is a view similar to Figure 7 showing in cross section therotor generated according to Figure 3.

Figure 10 is a diagram. similar to Figures 6 and 8 showing yet anothermethod of generating a rotor surface.

:2 In 4 ti a: :41 is Q Figure 11 is a diagram in cross section of throtor surface generated according to Figure 10?.

Figure 12 is a diagram to assist in an under standing of Figures 6 to 11inclusive.

Figure 13 is a view similar to Figures 6, 8 and it} showing how a fiatpump element is genera-ted? Figure 14 is a diagram in cross section of drotor generated according to Figure 13. 7

Figure 15 is another diagram to assist in art understanding of thegeneration of a rotor sur face. Figure 16 is a plan view of a statorshowing a number of generating semi-circles superim-i posed thereupon. 7

Figure 17 is a perspective view of a pair of semi-circles such as areused in generating the stator surface of Figure 16.

Figure 18 is a fragmentary cross sectional view of a pair of pumpingelements in cooperating relationship but showing a different embodimentfrom Figure 1.

Figures 19, 20 and 21 are diagrams useful in connection with anunderstanding of the generation of the stator surface.

A pump such as the one in which the rotors and stators hereinafter to bedescribed and claimed may be used is shown in cross section in Figure 1.The rotor is indicated at H), and it has a single spiral thread, thecrest of which is indicated in Figure 2 at H; The stator is indicated at12 and has a double spiral thread as indicated by the crests l3 and M.As shown in Figure 1, the stator 12 may be secured by bolting to a headl5 as indicated at IS. The head 15 may be provided with a port fittingI! having the thread I8 for attachment to a pipe. The stator [2 has acentral hole IQ for the passage of fluid which is being pumped.

The casing of the pump 20 may, as shown, consist of a ring 21 and aplate 22 welded together and bolted to the head [5 by means of bolts 23.A sleeve 24 may be welded or otherwise suitably attached to the plate 22to serve to hold the shaft bearing 25 for the drive shaft 2-6. It willbe clear that the casing consisting of the members 2 l, 22 and 24 couldbe cast from a single piece of metal if desired. Suitable sealing meansare provided as at 21 to seal the shaft 26 against the sleeve 24. Thecasing is provided with the exhaust port 24. Because of the compoundmovement of the rotor with respect to the stator, universal joint meansmust be provided for driving the rotor from the shaft 28 which rotateson a fixed axis. Therefore bolts 28 secure a cup-like member 29 to therotor Ill. The member 29 is provided with an. accurately dimensionedhole 3 30 and the end of the drive shaft 26 has a portion 31 of reduceddiameter and terminates in a spherical portion 32. Rotation istransmitted from the shaft 26 to the rotor by means of a pin 33 which issecured in diametrically opposed holes in the member 29 and which passesthrough a slot 34 in the ball 32. The slot 34 is of a width (in a planeperpendicular to the paper) to snugly accommodate the pin 33 and of awidth (in the plane of the paper at its center) to snugly accommodatethe pin 33. The slot 34 however flares at both ends to permit the cupand rotor and the pin 33 secured thereto to tilt with respect.

to the ball 32 and shaft 26. The particular movement as will appear moreclearly hereinafter involves the rotation of the rotor about a tiltedaxis wherein the tilted axis moves azimuthally, or nutates, in adirection opposite to the direction of rotation of the rotor. Themovement of the tilted axis is analogous to the movement of the axis ofa dying top except that the angle of tilt remains constant.

Coming now to a specific description of the surfaces of the rotor andstator and to a description of the manner in which these surfaces aregenerated, Figures 6 to 15 inclusive have to do with the generation ofrotor surfaces, and several embodiments of rotor surfaces are shown.Referring first to Figure 6, I have shown at 35 a cone and at 36 anelement of the cone 35. At 3'! I have indicated (in edge View) a circlein a plane perpendicular to the element 36 and drawn about the element36 as a center. Let it now be assumed that the element 36 is slowlycaused to move around the surface of the cone 35 and that while theelement 36 is so moving the length of the element is gradually increasedand that, at the same time, the diameter of the circle 31 i constantlybeing increased. As these various movements are taking place the points38 and 39 move respectively and successively (using 180 intervals forpurposes of the illustration to the points 38, 39', 38", 39", 38", 39",38 39 38", 39 and a surface will be generated which in cross sectionwill appear as shown in Figure 7.

It was mentioned above that the length of the element 36 of the cone 35was changing constantly and that the diameter of the circle 31 was alsochanging constantly, and it has been assumed in Figures 6 and 7 that thechanges in length of the element and diameter of the circle areproportional. The rotor element, produced as shown in Figure 7, I havedesignated as a conetype of rotor.

If the changes of diameter of the circle and length of the element arenon-proportional, as shown in Figures 8 and 9, the rotor surfaceproduced is what I have designated a bowl-type, as long as the increasein diameter of the circle is more rapid than the increase in the lengthof the element. If the increase in the length of the element is morerapid than the increase in diameter of the circle, then a flare-type ofrotor is produced a shown in Figures 10 and 11. Referring moreparticularly to the graph of Figure 12 where I have plotted diameter ofthe ring or circle against length of the element, the solid lineindicates the proportional increase of the two variables which producesthe cone-type of pump. The upper broken curve line indicates thesituation in the production of the bowl-type of rotor and the lowerbroken line indicates the situation in the formation of a flare-type ofrotor. For convenience the same numerals have been used in Figures 8 and10 as wereused in Figure 6.

If, on the other hand, the length of the element is maintained constantand the only change is in the diameter of the generating circle, thenthe situation will be as shown in Figures 13 and 14 and the rotorgenerated will be what I have called a fiat rotor. Here again the conehas been designated at 35 and the element at 36. The circle is againindicated at 31 and the progress of the points 38 and 39 is illustratedas before. The rotor surfaces produced according to Figures 6, 8, l0 and13 are shown respectively in the cross sectional diagrams of Figures 7,9, 11 and 14.

The diagram of Figure 15 shows in perspective the trace of the highpoints of the generating circle 31 which trace is shown in broken linesat 40, and it will be clear from the consideration of Figure 15 inconnection with the above described figures that in all of these cases agenerally spiral thread is produced.

The views of Figures 6, 7, 8, 9, 10 and 11 have been somewhatexaggerated in that actually there will not be as much differencebetween the fiat pump and the cone, bowl and fiare shaped pumps asappear in the drawing. This has been done to facilitate an understandingof how the surfaces are generated. The pumping elements can be generallydescribed as relatively flat, disc-like members with generally spiralthreads.

It will also be observed that while in Figures 6 to 11 inclusive boththe length of the generating element and the diameter of the generatingcircle are changing, in the arrangement of Figures 13 and 14 only thediameter of the generating circle is changing. However, in all cases thedistance from the apex of the cone to any point on the periphery of thecircle is changing and therefore the change which is taking place can bedefined generically as a change in the distance from the apex of thegenerating cone to a point on the periphery of the generating circle.The change in this dimension may result either from a change in thedimension of the circle alone or from a change in the dimension of thecircle and the length of the element together.

Figures 16 to 21 inclusive show the manner in which a stator surface isgenerated. In its broadest and most generic aspect let us assume a pairof semi-circles as indicated in Figures 19, 20 and 21 at 41 and 42.These semi-circles are of the same diameter and are connected by arectangular portion of a cylinder, as indicated at 43. The semi-circles4! and 42 are in planes at a fixed angle to each other, and thecylindrical surface 43 is tangent to the planes in which lie thesemi-circles 4i and 42 at the diameters of the semi-circles. Thus thesurfaces 4| and 43 are tangent at the line 44 and the surfaces 42 and 43are tangent at the line 45. In connection with this figure there must beassumed a fixed point 4'6 which is equidistant from every point on theperiphery of the figure. Since the portion 43 is cylindrical, it will beclear that any portion on the edge of the cylindrical connecting portionwill be equidistant from a point 46 as indicated by the arrow 47. Sincethe semi-circles 4| and 42 are in planes which are tangent at thediameters to the cylindrical surface 43, all points on the semi-circularportion of the periphery of the figure will be equidistant from thepoint 46 as indicated by the arrows at 48 and 49. Thus every pointaround the periphery of the figure is equidistant from a point 46. Ifnow the figure be rotated about an axis passing through the fixed point46, while the distance 41, 48 or 49 is continually changing, adoublethreaded surface will be generated. Here'again, as was pointed out inconnection with the rotors, the distance from the fixed point 46 to anypoint on the periphery of the figure can change for two reasons: It canchange first because the radius of the cylinder is changing and it canchange second because the diameters of the semicircles are changing andit can change third because both the radius of the cylinder and thediameters of the semi-circles are changing. As before, if the change ofthe two variables is proportional, there will be produced a cone-typestator whereas if the change is not proportional, there will be producedeither a bowl or a flaretype stator, depending upon whether thediameters of the semi-circles are increasing more rapidly or lessrapidly than the radius of the cylinder. Again, as in connection withthe rotors described. above,- if the radius of the cylinder reduces toso that the diameters 44 and 45 of the semi-circles 4| and 42 cometogether and coincide, as shown in Figure 17, there will be produced afiat stator, as illustrated in Figure 16. In Figure .16 there has beensuperimposed upon the figure of the stator a folded ring such as that ofFigure 17 wherein there are the semicircles 4| and 42 wherein the highpoints, i. e. the opposite ends of the mutual or common diameter, areindicated at 59' and 5!. There has also been superimposed on the figurea pair of semi-circles 4| and 42' having their high points at 50 and 5|.With what has been said before in connection with the rotors, it will beclear how the figures described generate the various forms of stators.

I have described above in considerable detail the generation of therotor and stator surfaces. It remains, however, to set forth theconditions which must prevail in order that a rotor and stator may worktogether as a pump for compressor or expander. It is necessary that theapex of the generating cone of the rotor must coincide with the fixedpoint of the stator (i. e. the apex of the cone 35 must coincide withthe point 46.). It is also necessary that the fixed angle of the statorgenerating surface must be twice. the apex angle of the cone. (Thedihedral angle between the surfaces il and 42 must be twice the apexangle of the cone 35. In other words, the angle of wobble of the rotorequals the apex angle of the cone). the length of the element of thecone equal the radius of the cylinder (thus the length of the element35must equal the radius of the cylindrical. portion 43). It is furthernecessary that the radius of the circle used in generating the rotorsurface be equal to the radii of the semi-circles used in generating thestator surface (thus the radius of the circle 3'! must equal the radiiof the semi-circles ll-42).

Finally it is necessary that the azimuthal angle of the generatingelement of the cone must at all times equal twice the azimuthal angle ofthe figure.

If the foregoing conditions are met in the generation of the rotor andstator surfaces then these surfaces will coact together to form acompressor or an expander, depending upon the constancy of the pitch.

In Figure 18 I have shown the working elementsof a cone-type pump whichare in all respects similar to those shown in Figure l where fiat typeelements are illustrated. The only difference in Figure 18 is that thehole through the rotor must be flared and the cup member 29' must beflared to permit of the It is necessary that rocking movement the same.Similar reference numerals have been used in Figure 18 as were used inFigure 1, except that the rotor and stator have been identifiedrespectively as It andIZ'. As was pointed out above, if the pitch of thethreads is constant the two elements will function either as acompressor or an expander depending upon the direction of movement ofthe pumping pocket, Whereas if the threads are distorted so that theirpitch is not constant but is less at the periphery than in the center,then a constant volume pump is provided.

It will be clear that various modifications in detail may be madewithout departing from the -spirit of my invention, and I therefore donot intend to limit myself except as set forth in the claims whichfollow.

Having now fully described my invention, what I claim as new and desireto secure by Letters Patent is:

1. A pumping member for a rotary pump comprising a disc-like memberhaving a spiral thread progressing outwardly from the axis, the surfaceof said member being approximately that generated by a circle about anelement of a cone in a plane perpendicular to said element, as saidelement is moved around the surface of said cone, accompanied by acontinuous change in the distance from the periphery of said circle tothe apex of said cone.

2. A pumping member according to claim 1, wherein the length of theelement of the cone is constant, and said change in distance resultsfrom a continuous change in the diameter of said circle;

3. A pumping member according to claim 1,

wherein the change in distance results from a continuous change in theposition of said circle along said element and a continuous change inthe diameter of said circle.

' 4. A pumping member according to claim 1, wherein the change indistance results from a continuous change in the position of said circlealong said element and a continuous proportional change in the diameterof said circle.

5. A pumping member according to claim' 1, wherein the change indistance results from a continuous change in the position of said circlealong said element and a continuous non-proportional change in thediameter of said circle.

6. A pumping member for a rotary pump comprising a disc-like memberhaving a double, spiral thread progressing outwardly from the axis, thesurface of said member being approximately that generated by a figurecomprising: two semi-circles in planes at a fixed angle to each otherconnected by a rectangular portion of a cylinder tangent to said planesat the diameters of said semi-circles, such that every point on theperiphery of said figure is at an equal distance from a fixed point;when said figure is rotated about an axis passing through said fixedpoint and the center of said figure, accompanied by a continuous changein the distance from said fixed point to a point on the periphery ofsaid figure.

7. A pumping member according to claim 6, wherein the radius of saidcylinder is constant, and the change in distance results from acontinuous change in the diameter of said semicircles and the axiallength of said portion of a cylinder.

8. A pumping member according to claim 6, wherein the change in distanceresults from a heretofore described. In other respects the universaljoint connection is.

continuous change in the radius of said cylinder and a continuous changein the diameter of said semi-circles and the axial length of saidportion of a cylinder.

9. A pumping member according to claim 6, wherein the change in distanceresults from a continuous change in the radius of said cylinder and acontinuous proportional change in the diameter of said semi-circles andthe axial length of said portion of a cylinder.

10. A pumping member according to claim 6, wherein the change indistance results from a continuous change in the radius of said cylinderand a continuous non-proportional change in the diameter of saidsemi-circles and the axial length of said portion of a cylinder.

11. A pump comprising a pair of pumping members, one of said membersbeing fixed, a shaft for driving the other of said members, the other ofsaid members being connected to said shaft by a universal joint, each ofsaid members being disc-like in shape, one of said members having aspiral thread progressing outwardly from its axis, and having a surfaceapproximately that generated by a circle about an element of a cone in aplane perpendicular to said element, as said element is moved around thesurface of said cone, accompanied by a continuous change in the distancefrom the periphery of said circle to the apex of said cone; the other ofsaid members having a double, spiral thread progressing outwardly fromits axis, and having a surface approximately that generated by a. figurecomprising: two semi-circles in planes at a fixed angle to each otherconnected by arectangular portion of a cylinder tangent to said planesat the diameters of said semi-circles, such that every point on theperiphery of said figure is an equal distance from a fixed point; whensaid figure is rotated about an axis passing through said fixed pointand the center of said figure, accompanied by a continuous change in thedistance from said fixed point to a point on the periphery of saidfigure; the relation between said members being approximately such thatthe apex of the generating cone of said one member is at the fixed pointof said other member, that the fixed angle of said other member is twicethe apex angle of said cone, that the length of the element of said coneequals the radius of said cylinder, that the radius of said circlesequal the radii of said semi-circles, and that the azimuthal angle ofthe generating element of said one member is at all times equal to twicethe azimuthal angle of said figure, and easing means enclosing saidmembers and having intake and exhaust ports and an entry aperture forsaid shaft.

' 12. .A pump according to claim 11, wherein the length of the saidelement of the cone, and the radius of said cylinder are constant, andthe changes in distance result respectively from a continuous change inthe diameter of said circle, and a continuous change in the diameter ofsaid semi-circles and the axial length of said portion of a cylinder.

13. A pump according to claim 11, wherein the changes in distance resultrespectively from: a continuous change in the position of said circlealong said element and a continuous change in the diameter of saidcircle; and from a continuous change in the radius of said cylinder anda continuous change in the diameter of said semicircles and the axiallength of said portion of a cylinder.

14. A pump according to claim 11, wherein the changes in distance resultrespectively from: a continuous change in the position of said circlealong said element and a continuous proportional change in the diameterof said circle; and from a continuous change in the radius of saidcylinder and a continuous proportional change in the diameter of saidsemi-circles and the axial length of said portion of a cylinder.

15. A pump according to claim 11, wherein the changes in distance resultrespectively from: a continuous change in the position of said circlealong said element and a continuous non-proportional change in thediameter of said circle; and from a continuous change in the radius ofsaid cylinder and a continuous non proportional change in the diameterof said semi-circles and the axial length of said portion of a cylinder.

SHELDON S. L. CHANG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 615,392 Kelley Dec. 6, 18981,389,189 Feuerheerd Aug. 30, 1921 2,212,417 George Aug. 20, 19402,324,168 Montelius July 13, 1943 2,353,373 Thompson July 11,19442,512,764 Byram June 27, 1950 FOREIGN PATENTS Number Country Date 28,560Denmark Sept. 21, 1921 367,086 Great Britain Feb. 18, 1932 129,104Austria July 11, 1932 441,528 Great Britain Jan. 21, 1936 622,583 GreatBritain May 4, 1949 813,559 France Mar. 1, 1937

